Development of a High Temperature Sensor Based on Transformation- Induced Resistivity

摘要

A thermal history sensor based on variations in physical properties accompanying microstructural changes in Ni-Ni3Al-based alloys has been demonstrated. The operation of such sensor is based on the established correlation between microhardness and/or electrical resistivity, and the material damage parameter, expressed in the form of Larson-Miller Parameter (LMP). From the characteristic LMP vs. property plot for the particular alloy, one can read the value of LMP and get a measure of the incurred material damage. Knowing the exposure time, the equivalent temperature can be calculated. Furthermore, it has been demonstrated that with a sensor comprised of two different alloys, the equivalent temperature and duration of the thermal exposures can be extracted independently from the microhardness data. The key attribute to extend this approach to a practical application is structural and compositional homogeneity of the sensor alloys. A process that yields such homogeneity will need to be identified. Thin film deposition techniques, plasma spray coating methods, laser deposition followed by well defined heat treatment are some processes that are suggested. Multiple sensors with varying chemistries and heat treatments will further improve the accuracy by reducing the effect of measurement errors and eliminating multiple possible solutions for a given sensor read-out.